It's really wonky to put on but it works. It also "kind of" works for Steam Deck OLED despite being billed for LCD models, and by "kind of" I mean the connector port doesn't latch in quite as it should, but it's still functional if plugged in. It will stay put if the machine isn't put under any extreme jostling or drops or anything, and it's easy to reattach it if it does (but you dropped it in this scenario, so you've probably got bigger problems). Get some sublimation tape to keep it down if you don't trust it, but it's screwed in tight enough there shouldn't be any problems; and reminder this is ONLY for a Steam Deck OLED, an LCD won't have these issues at all because of the proper connector type.

It bears mentioning:

Watch the installation guide! Otherwise you won't know what the two plastic rings on a sticker sheet it comes with are for.

You CANNOT get around using the membranes provided for the buttons and d-pad provided. The thinner membrane is needed because the clicky switches create clearance issues with the d-pad if you try to use the original membranes.

The PCBs for both the original d-pad and button pads and the replacement clicky pads are a thin "sticker" attached to the framework that makes up the analog triggers and shoulder bumpers. Be extremely careful in removing the PCBs if you want to preserve them or change them back.

It's kind of a sidegrade rather than an upgrade, really. It ain't no Vita d-pad (that would be dome switches + rubber membrane, not mouse click switches) but it gives a much more definite tactile sensation. People complain the Steam Deck's d-pad is "mushy" but I don't feel it any more than I would for a SNES controller.